Ignoring the New Zealand Rugby Union and players' association directive to use a mouthguard is one thing - ignoring the All Blacks coach is another matter.

Steve Hansen has made it clear that he expects his players to use a mouthguard during tomorrow night's Bledisloe Cup rugby test against Australia.

"Did we have some that didn't wear mouthguards? Oh, I didn't know that," Hansen said yesterday when asked why some players did not comply with the directive in the test against South Africa at Ellis Park.

"They'd be dumb if they didn't have mouthguards, as far as I'm concerned. I didn't wear one once and ended up with 14 stitches in my mouth from putting my teeth through my lip, so I'll be recommending they wear one.

"But you know what young men are like. They do what they think is best for them."

Israel Dagg, Ben Smith, Ben Franks and Julian Savea have been pictured playing for the All Blacks with no mouthguard.

Dagg had his mouth bloodied early in the epic test win over the Springboks in Johannesburg.

While it is not mandatory under International Rugby Board rules to use a mouthguard during tests, the NZRU players' collective agreement requires all its players to do so.

The issue came to light when referee Nick Briant sent Wellington players Tomasi Palu and Ardie Savea from the field to fetch mouthguards during an NPC match this season.

NZRU professional rugby general manager Neil Sorensen and New Zealand Rugby Players' Association chief executive Rob Nichol have said they expected the All Blacks to comply.

Sorensen said he expected the All Blacks players and management to discuss the issue before their last test outing in South Africa, but Dagg was among those to go without.

Passing on Sorensen's message has clearly not been a priority.

"The laws of the game say they have to wear one, don't they?" Hansen said.

"I'm not sure there are too many who don't wear one but I'll find out. I'll get [media manager] Joe [Locke] to ask them and we'll get them a mouthguard."